Confocal or two-photon laser scanning microscopes usually adopt one of two scanning modes. One utilizes two Galvanometer scanning mirrors (hereafter refers as GG mode) to steer laser beam in orthogonal axes in a raster pattern to cover a rectangular area. The other utilizes one Resonant scanning mirror to steer laser beam in one axis and a Galvanometer scanning mirror in the orthogonal axis (hereafter refers as RG mode). In the GG mode, user defines the laser beam scanning trajectory which is restricted by certain angular acceleration. In the RG mode, the resonant scanning mirror scans several folds faster than Galvanometers while runs in sinusoid at a fixed frequency. In other words, the RG mode scans much faster than the GG mode yet lacks the flexibility of defining the scanning trajectory. It is therefore advantageous to combine the two modes in one (hereafter refers as RGG mode) thus user is capable of running fast scans at defined position or along defined path. In practice, how to fit all components in a compact enclosure without sacrificing performance is not trivial. An ideal optomechanical design needs to consider the clear aperture, the mirror shape, the air space between mirrors, a relatively large scanning angle, an optical system for scanning conjugation, nice noise isolation, and a user-friendly interface.
Therefore, there is long-felt need for a design of RGG scan head that overcomes the technical hurdles discussed above.